4 TGSI, Tungsten Graphics Shader Infrastructure, is an intermediate language
5 for describing shaders. Since Gallium is inherently shaderful, shaders are
6 an important part of the API. TGSI is the only intermediate representation
12 All TGSI instructions, known as *opcodes*, operate on arbitrary-precision
13 floating-point four-component vectors. An opcode may have up to one
14 destination register, known as *dst*, and between zero and three source
15 registers, called *src0* through *src2*, or simply *src* if there is only
18 Some instructions, like :opcode:`I2F`, permit re-interpretation of vector
19 components as integers. Other instructions permit using registers as
20 two-component vectors with double precision; see :ref:`doubleopcodes`.
22 When an instruction has a scalar result, the result is usually copied into
23 each of the components of *dst*. When this happens, the result is said to be
24 *replicated* to *dst*. :opcode:`RCP` is one such instruction.
29 TGSI supports modifiers on inputs (as well as saturate modifier on instructions).
31 For inputs which have a floating point type, both absolute value and negation
32 modifiers are supported (with absolute value being applied first).
33 TGSI_OPCODE_MOV is considered to have float input type for applying modifiers.
35 For inputs which have signed or unsigned type only the negate modifier is
42 ^^^^^^^^^^^^^^^^^^^^^^^^^
44 These opcodes are guaranteed to be available regardless of the driver being
47 .. opcode:: ARL - Address Register Load
51 dst.x = \lfloor src.x\rfloor
53 dst.y = \lfloor src.y\rfloor
55 dst.z = \lfloor src.z\rfloor
57 dst.w = \lfloor src.w\rfloor
60 .. opcode:: MOV - Move
73 .. opcode:: LIT - Light Coefficients
78 dst.y &= max(src.x, 0) \\
79 dst.z &= (src.x > 0) ? max(src.y, 0)^{clamp(src.w, -128, 128))} : 0 \\
83 .. opcode:: RCP - Reciprocal
85 This instruction replicates its result.
92 .. opcode:: RSQ - Reciprocal Square Root
94 This instruction replicates its result. The results are undefined for src <= 0.
98 dst = \frac{1}{\sqrt{src.x}}
101 .. opcode:: SQRT - Square Root
103 This instruction replicates its result. The results are undefined for src < 0.
110 .. opcode:: EXP - Approximate Exponential Base 2
114 dst.x &= 2^{\lfloor src.x\rfloor} \\
115 dst.y &= src.x - \lfloor src.x\rfloor \\
116 dst.z &= 2^{src.x} \\
120 .. opcode:: LOG - Approximate Logarithm Base 2
124 dst.x &= \lfloor\log_2{|src.x|}\rfloor \\
125 dst.y &= \frac{|src.x|}{2^{\lfloor\log_2{|src.x|}\rfloor}} \\
126 dst.z &= \log_2{|src.x|} \\
130 .. opcode:: MUL - Multiply
134 dst.x = src0.x \times src1.x
136 dst.y = src0.y \times src1.y
138 dst.z = src0.z \times src1.z
140 dst.w = src0.w \times src1.w
143 .. opcode:: ADD - Add
147 dst.x = src0.x + src1.x
149 dst.y = src0.y + src1.y
151 dst.z = src0.z + src1.z
153 dst.w = src0.w + src1.w
156 .. opcode:: DP3 - 3-component Dot Product
158 This instruction replicates its result.
162 dst = src0.x \times src1.x + src0.y \times src1.y + src0.z \times src1.z
165 .. opcode:: DP4 - 4-component Dot Product
167 This instruction replicates its result.
171 dst = src0.x \times src1.x + src0.y \times src1.y + src0.z \times src1.z + src0.w \times src1.w
174 .. opcode:: DST - Distance Vector
179 dst.y &= src0.y \times src1.y\\
184 .. opcode:: MIN - Minimum
188 dst.x = min(src0.x, src1.x)
190 dst.y = min(src0.y, src1.y)
192 dst.z = min(src0.z, src1.z)
194 dst.w = min(src0.w, src1.w)
197 .. opcode:: MAX - Maximum
201 dst.x = max(src0.x, src1.x)
203 dst.y = max(src0.y, src1.y)
205 dst.z = max(src0.z, src1.z)
207 dst.w = max(src0.w, src1.w)
210 .. opcode:: SLT - Set On Less Than
214 dst.x = (src0.x < src1.x) ? 1.0F : 0.0F
216 dst.y = (src0.y < src1.y) ? 1.0F : 0.0F
218 dst.z = (src0.z < src1.z) ? 1.0F : 0.0F
220 dst.w = (src0.w < src1.w) ? 1.0F : 0.0F
223 .. opcode:: SGE - Set On Greater Equal Than
227 dst.x = (src0.x >= src1.x) ? 1.0F : 0.0F
229 dst.y = (src0.y >= src1.y) ? 1.0F : 0.0F
231 dst.z = (src0.z >= src1.z) ? 1.0F : 0.0F
233 dst.w = (src0.w >= src1.w) ? 1.0F : 0.0F
236 .. opcode:: MAD - Multiply And Add
240 dst.x = src0.x \times src1.x + src2.x
242 dst.y = src0.y \times src1.y + src2.y
244 dst.z = src0.z \times src1.z + src2.z
246 dst.w = src0.w \times src1.w + src2.w
249 .. opcode:: SUB - Subtract
253 dst.x = src0.x - src1.x
255 dst.y = src0.y - src1.y
257 dst.z = src0.z - src1.z
259 dst.w = src0.w - src1.w
262 .. opcode:: LRP - Linear Interpolate
266 dst.x = src0.x \times src1.x + (1 - src0.x) \times src2.x
268 dst.y = src0.y \times src1.y + (1 - src0.y) \times src2.y
270 dst.z = src0.z \times src1.z + (1 - src0.z) \times src2.z
272 dst.w = src0.w \times src1.w + (1 - src0.w) \times src2.w
275 .. opcode:: CND - Condition
279 dst.x = (src2.x > 0.5) ? src0.x : src1.x
281 dst.y = (src2.y > 0.5) ? src0.y : src1.y
283 dst.z = (src2.z > 0.5) ? src0.z : src1.z
285 dst.w = (src2.w > 0.5) ? src0.w : src1.w
288 .. opcode:: DP2A - 2-component Dot Product And Add
292 dst.x = src0.x \times src1.x + src0.y \times src1.y + src2.x
294 dst.y = src0.x \times src1.x + src0.y \times src1.y + src2.x
296 dst.z = src0.x \times src1.x + src0.y \times src1.y + src2.x
298 dst.w = src0.x \times src1.x + src0.y \times src1.y + src2.x
301 .. opcode:: FRC - Fraction
305 dst.x = src.x - \lfloor src.x\rfloor
307 dst.y = src.y - \lfloor src.y\rfloor
309 dst.z = src.z - \lfloor src.z\rfloor
311 dst.w = src.w - \lfloor src.w\rfloor
314 .. opcode:: CLAMP - Clamp
318 dst.x = clamp(src0.x, src1.x, src2.x)
320 dst.y = clamp(src0.y, src1.y, src2.y)
322 dst.z = clamp(src0.z, src1.z, src2.z)
324 dst.w = clamp(src0.w, src1.w, src2.w)
327 .. opcode:: FLR - Floor
329 This is identical to :opcode:`ARL`.
333 dst.x = \lfloor src.x\rfloor
335 dst.y = \lfloor src.y\rfloor
337 dst.z = \lfloor src.z\rfloor
339 dst.w = \lfloor src.w\rfloor
342 .. opcode:: ROUND - Round
355 .. opcode:: EX2 - Exponential Base 2
357 This instruction replicates its result.
364 .. opcode:: LG2 - Logarithm Base 2
366 This instruction replicates its result.
373 .. opcode:: POW - Power
375 This instruction replicates its result.
379 dst = src0.x^{src1.x}
381 .. opcode:: XPD - Cross Product
385 dst.x = src0.y \times src1.z - src1.y \times src0.z
387 dst.y = src0.z \times src1.x - src1.z \times src0.x
389 dst.z = src0.x \times src1.y - src1.x \times src0.y
394 .. opcode:: ABS - Absolute
407 .. opcode:: RCC - Reciprocal Clamped
409 This instruction replicates its result.
411 XXX cleanup on aisle three
415 dst = (1 / src.x) > 0 ? clamp(1 / src.x, 5.42101e-020, 1.84467e+019) : clamp(1 / src.x, -1.84467e+019, -5.42101e-020)
418 .. opcode:: DPH - Homogeneous Dot Product
420 This instruction replicates its result.
424 dst = src0.x \times src1.x + src0.y \times src1.y + src0.z \times src1.z + src1.w
427 .. opcode:: COS - Cosine
429 This instruction replicates its result.
436 .. opcode:: DDX - Derivative Relative To X
440 dst.x = partialx(src.x)
442 dst.y = partialx(src.y)
444 dst.z = partialx(src.z)
446 dst.w = partialx(src.w)
449 .. opcode:: DDY - Derivative Relative To Y
453 dst.x = partialy(src.x)
455 dst.y = partialy(src.y)
457 dst.z = partialy(src.z)
459 dst.w = partialy(src.w)
462 .. opcode:: PK2H - Pack Two 16-bit Floats
467 .. opcode:: PK2US - Pack Two Unsigned 16-bit Scalars
472 .. opcode:: PK4B - Pack Four Signed 8-bit Scalars
477 .. opcode:: PK4UB - Pack Four Unsigned 8-bit Scalars
482 .. opcode:: RFL - Reflection Vector
486 dst.x = 2 \times (src0.x \times src1.x + src0.y \times src1.y + src0.z \times src1.z) / (src0.x \times src0.x + src0.y \times src0.y + src0.z \times src0.z) \times src0.x - src1.x
488 dst.y = 2 \times (src0.x \times src1.x + src0.y \times src1.y + src0.z \times src1.z) / (src0.x \times src0.x + src0.y \times src0.y + src0.z \times src0.z) \times src0.y - src1.y
490 dst.z = 2 \times (src0.x \times src1.x + src0.y \times src1.y + src0.z \times src1.z) / (src0.x \times src0.x + src0.y \times src0.y + src0.z \times src0.z) \times src0.z - src1.z
496 Considered for removal.
499 .. opcode:: SEQ - Set On Equal
503 dst.x = (src0.x == src1.x) ? 1.0F : 0.0F
505 dst.y = (src0.y == src1.y) ? 1.0F : 0.0F
507 dst.z = (src0.z == src1.z) ? 1.0F : 0.0F
509 dst.w = (src0.w == src1.w) ? 1.0F : 0.0F
512 .. opcode:: SFL - Set On False
514 This instruction replicates its result.
522 Considered for removal.
525 .. opcode:: SGT - Set On Greater Than
529 dst.x = (src0.x > src1.x) ? 1.0F : 0.0F
531 dst.y = (src0.y > src1.y) ? 1.0F : 0.0F
533 dst.z = (src0.z > src1.z) ? 1.0F : 0.0F
535 dst.w = (src0.w > src1.w) ? 1.0F : 0.0F
538 .. opcode:: SIN - Sine
540 This instruction replicates its result.
547 .. opcode:: SLE - Set On Less Equal Than
551 dst.x = (src0.x <= src1.x) ? 1.0F : 0.0F
553 dst.y = (src0.y <= src1.y) ? 1.0F : 0.0F
555 dst.z = (src0.z <= src1.z) ? 1.0F : 0.0F
557 dst.w = (src0.w <= src1.w) ? 1.0F : 0.0F
560 .. opcode:: SNE - Set On Not Equal
564 dst.x = (src0.x != src1.x) ? 1.0F : 0.0F
566 dst.y = (src0.y != src1.y) ? 1.0F : 0.0F
568 dst.z = (src0.z != src1.z) ? 1.0F : 0.0F
570 dst.w = (src0.w != src1.w) ? 1.0F : 0.0F
573 .. opcode:: STR - Set On True
575 This instruction replicates its result.
582 .. opcode:: TEX - Texture Lookup
584 for array textures src0.y contains the slice for 1D,
585 and src0.z contain the slice for 2D.
587 for shadow textures with no arrays, src0.z contains
590 for shadow textures with arrays, src0.z contains
591 the reference value for 1D arrays, and src0.w contains
592 the reference value for 2D arrays.
594 There is no way to pass a bias in the .w value for
595 shadow arrays, and GLSL doesn't allow this.
596 GLSL does allow cube shadows maps to take a bias value,
597 and we have to determine how this will look in TGSI.
605 dst = texture\_sample(unit, coord, bias)
607 .. opcode:: TXD - Texture Lookup with Derivatives
619 dst = texture\_sample\_deriv(unit, coord, bias, ddx, ddy)
622 .. opcode:: TXP - Projective Texture Lookup
626 coord.x = src0.x / src.w
628 coord.y = src0.y / src.w
630 coord.z = src0.z / src.w
636 dst = texture\_sample(unit, coord, bias)
639 .. opcode:: UP2H - Unpack Two 16-Bit Floats
645 Considered for removal.
647 .. opcode:: UP2US - Unpack Two Unsigned 16-Bit Scalars
653 Considered for removal.
655 .. opcode:: UP4B - Unpack Four Signed 8-Bit Values
661 Considered for removal.
663 .. opcode:: UP4UB - Unpack Four Unsigned 8-Bit Scalars
669 Considered for removal.
671 .. opcode:: X2D - 2D Coordinate Transformation
675 dst.x = src0.x + src1.x \times src2.x + src1.y \times src2.y
677 dst.y = src0.y + src1.x \times src2.z + src1.y \times src2.w
679 dst.z = src0.x + src1.x \times src2.x + src1.y \times src2.y
681 dst.w = src0.y + src1.x \times src2.z + src1.y \times src2.w
685 Considered for removal.
688 .. opcode:: ARA - Address Register Add
694 Considered for removal.
696 .. opcode:: ARR - Address Register Load With Round
709 .. opcode:: SSG - Set Sign
713 dst.x = (src.x > 0) ? 1 : (src.x < 0) ? -1 : 0
715 dst.y = (src.y > 0) ? 1 : (src.y < 0) ? -1 : 0
717 dst.z = (src.z > 0) ? 1 : (src.z < 0) ? -1 : 0
719 dst.w = (src.w > 0) ? 1 : (src.w < 0) ? -1 : 0
722 .. opcode:: CMP - Compare
726 dst.x = (src0.x < 0) ? src1.x : src2.x
728 dst.y = (src0.y < 0) ? src1.y : src2.y
730 dst.z = (src0.z < 0) ? src1.z : src2.z
732 dst.w = (src0.w < 0) ? src1.w : src2.w
735 .. opcode:: KILL_IF - Conditional Discard
737 Conditional discard. Allowed in fragment shaders only.
741 if (src.x < 0 || src.y < 0 || src.z < 0 || src.w < 0)
746 .. opcode:: KILL - Discard
748 Unconditional discard. Allowed in fragment shaders only.
751 .. opcode:: SCS - Sine Cosine
764 .. opcode:: TXB - Texture Lookup With Bias
778 dst = texture\_sample(unit, coord, bias)
781 .. opcode:: NRM - 3-component Vector Normalise
785 dst.x = src.x / (src.x \times src.x + src.y \times src.y + src.z \times src.z)
787 dst.y = src.y / (src.x \times src.x + src.y \times src.y + src.z \times src.z)
789 dst.z = src.z / (src.x \times src.x + src.y \times src.y + src.z \times src.z)
794 .. opcode:: DIV - Divide
798 dst.x = \frac{src0.x}{src1.x}
800 dst.y = \frac{src0.y}{src1.y}
802 dst.z = \frac{src0.z}{src1.z}
804 dst.w = \frac{src0.w}{src1.w}
807 .. opcode:: DP2 - 2-component Dot Product
809 This instruction replicates its result.
813 dst = src0.x \times src1.x + src0.y \times src1.y
816 .. opcode:: TXL - Texture Lookup With explicit LOD
830 dst = texture\_sample(unit, coord, lod)
833 .. opcode:: PUSHA - Push Address Register On Stack
842 Considered for cleanup.
846 Considered for removal.
848 .. opcode:: POPA - Pop Address Register From Stack
857 Considered for cleanup.
861 Considered for removal.
864 .. opcode:: BRA - Branch
870 Considered for removal.
873 .. opcode:: CALLNZ - Subroutine Call If Not Zero
879 Considered for cleanup.
883 Considered for removal.
887 ^^^^^^^^^^^^^^^^^^^^^^^^
889 These opcodes are primarily provided for special-use computational shaders.
890 Support for these opcodes indicated by a special pipe capability bit (TBD).
892 XXX doesn't look like most of the opcodes really belong here.
894 .. opcode:: CEIL - Ceiling
898 dst.x = \lceil src.x\rceil
900 dst.y = \lceil src.y\rceil
902 dst.z = \lceil src.z\rceil
904 dst.w = \lceil src.w\rceil
907 .. opcode:: TRUNC - Truncate
920 .. opcode:: MOD - Modulus
924 dst.x = src0.x \bmod src1.x
926 dst.y = src0.y \bmod src1.y
928 dst.z = src0.z \bmod src1.z
930 dst.w = src0.w \bmod src1.w
933 .. opcode:: UARL - Integer Address Register Load
935 Moves the contents of the source register, assumed to be an integer, into the
936 destination register, which is assumed to be an address (ADDR) register.
939 .. opcode:: SAD - Sum Of Absolute Differences
943 dst.x = |src0.x - src1.x| + src2.x
945 dst.y = |src0.y - src1.y| + src2.y
947 dst.z = |src0.z - src1.z| + src2.z
949 dst.w = |src0.w - src1.w| + src2.w
952 .. opcode:: TXF - Texel Fetch
954 As per NV_gpu_shader4, extract a single texel from a specified texture
955 image. The source sampler may not be a CUBE or SHADOW. src 0 is a
956 four-component signed integer vector used to identify the single texel
957 accessed. 3 components + level. src 1 is a 3 component constant signed
958 integer vector, with each component only have a range of -8..+8 (hw only
959 seems to deal with this range, interface allows for up to unsigned int).
960 TXF(uint_vec coord, int_vec offset).
963 .. opcode:: TXQ - Texture Size Query
965 As per NV_gpu_program4, retrieve the dimensions of the texture depending on
966 the target. For 1D (width), 2D/RECT/CUBE (width, height), 3D (width, height,
967 depth), 1D array (width, layers), 2D array (width, height, layers)
973 dst.x = texture\_width(unit, lod)
975 dst.y = texture\_height(unit, lod)
977 dst.z = texture\_depth(unit, lod)
979 .. opcode:: TG4 - Texture Gather
981 As per ARB_texture_gather, gathers the four texels to be used in a bi-linear
982 filtering operation and packs them into a single register. Only works with
983 2D, 2D array, cubemaps, and cubemaps arrays. For 2D textures, only the
984 addressing modes of the sampler and the top level of any mip pyramid are
985 used. Set W to zero. It behaves like the TEX instruction, but a filtered
986 sample is not generated. The four samples that contribute to filtering are
987 placed into xyzw in clockwise order, starting with the (u,v) texture
988 coordinate delta at the following locations (-, +), (+, +), (+, -), (-, -),
989 where the magnitude of the deltas are half a texel.
991 PIPE_CAP_TEXTURE_SM5 enhances this instruction to support shadow per-sample
992 depth compares, single component selection, and a non-constant offset. It
993 doesn't allow support for the GL independent offset to get i0,j0. This would
994 require another CAP is hw can do it natively. For now we lower that before
1003 dst = texture\_gather4 (unit, coord, component)
1005 (with SM5 - cube array shadow)
1013 dst = texture\_gather (uint, coord, compare)
1015 .. opcode:: LODQ - level of detail query
1017 Compute the LOD information that the texture pipe would use to access the
1018 texture. The Y component contains the computed LOD lambda_prime. The X
1019 component contains the LOD that will be accessed, based on min/max lod's
1026 dst.xy = lodq(uint, coord);
1029 ^^^^^^^^^^^^^^^^^^^^^^^^
1030 These opcodes are used for integer operations.
1031 Support for these opcodes indicated by PIPE_SHADER_CAP_INTEGERS (all of them?)
1034 .. opcode:: I2F - Signed Integer To Float
1036 Rounding is unspecified (round to nearest even suggested).
1040 dst.x = (float) src.x
1042 dst.y = (float) src.y
1044 dst.z = (float) src.z
1046 dst.w = (float) src.w
1049 .. opcode:: U2F - Unsigned Integer To Float
1051 Rounding is unspecified (round to nearest even suggested).
1055 dst.x = (float) src.x
1057 dst.y = (float) src.y
1059 dst.z = (float) src.z
1061 dst.w = (float) src.w
1064 .. opcode:: F2I - Float to Signed Integer
1066 Rounding is towards zero (truncate).
1067 Values outside signed range (including NaNs) produce undefined results.
1080 .. opcode:: F2U - Float to Unsigned Integer
1082 Rounding is towards zero (truncate).
1083 Values outside unsigned range (including NaNs) produce undefined results.
1087 dst.x = (unsigned) src.x
1089 dst.y = (unsigned) src.y
1091 dst.z = (unsigned) src.z
1093 dst.w = (unsigned) src.w
1096 .. opcode:: UADD - Integer Add
1098 This instruction works the same for signed and unsigned integers.
1099 The low 32bit of the result is returned.
1103 dst.x = src0.x + src1.x
1105 dst.y = src0.y + src1.y
1107 dst.z = src0.z + src1.z
1109 dst.w = src0.w + src1.w
1112 .. opcode:: UMAD - Integer Multiply And Add
1114 This instruction works the same for signed and unsigned integers.
1115 The multiplication returns the low 32bit (as does the result itself).
1119 dst.x = src0.x \times src1.x + src2.x
1121 dst.y = src0.y \times src1.y + src2.y
1123 dst.z = src0.z \times src1.z + src2.z
1125 dst.w = src0.w \times src1.w + src2.w
1128 .. opcode:: UMUL - Integer Multiply
1130 This instruction works the same for signed and unsigned integers.
1131 The low 32bit of the result is returned.
1135 dst.x = src0.x \times src1.x
1137 dst.y = src0.y \times src1.y
1139 dst.z = src0.z \times src1.z
1141 dst.w = src0.w \times src1.w
1144 .. opcode:: IMUL_HI - Signed Integer Multiply High Bits
1146 The high 32bits of the multiplication of 2 signed integers are returned.
1150 dst.x = (src0.x \times src1.x) >> 32
1152 dst.y = (src0.y \times src1.y) >> 32
1154 dst.z = (src0.z \times src1.z) >> 32
1156 dst.w = (src0.w \times src1.w) >> 32
1159 .. opcode:: UMUL_HI - Unsigned Integer Multiply High Bits
1161 The high 32bits of the multiplication of 2 unsigned integers are returned.
1165 dst.x = (src0.x \times src1.x) >> 32
1167 dst.y = (src0.y \times src1.y) >> 32
1169 dst.z = (src0.z \times src1.z) >> 32
1171 dst.w = (src0.w \times src1.w) >> 32
1174 .. opcode:: IDIV - Signed Integer Division
1176 TBD: behavior for division by zero.
1180 dst.x = src0.x \ src1.x
1182 dst.y = src0.y \ src1.y
1184 dst.z = src0.z \ src1.z
1186 dst.w = src0.w \ src1.w
1189 .. opcode:: UDIV - Unsigned Integer Division
1191 For division by zero, 0xffffffff is returned.
1195 dst.x = src0.x \ src1.x
1197 dst.y = src0.y \ src1.y
1199 dst.z = src0.z \ src1.z
1201 dst.w = src0.w \ src1.w
1204 .. opcode:: UMOD - Unsigned Integer Remainder
1206 If second arg is zero, 0xffffffff is returned.
1210 dst.x = src0.x \ src1.x
1212 dst.y = src0.y \ src1.y
1214 dst.z = src0.z \ src1.z
1216 dst.w = src0.w \ src1.w
1219 .. opcode:: NOT - Bitwise Not
1232 .. opcode:: AND - Bitwise And
1236 dst.x = src0.x \& src1.x
1238 dst.y = src0.y \& src1.y
1240 dst.z = src0.z \& src1.z
1242 dst.w = src0.w \& src1.w
1245 .. opcode:: OR - Bitwise Or
1249 dst.x = src0.x | src1.x
1251 dst.y = src0.y | src1.y
1253 dst.z = src0.z | src1.z
1255 dst.w = src0.w | src1.w
1258 .. opcode:: XOR - Bitwise Xor
1262 dst.x = src0.x \oplus src1.x
1264 dst.y = src0.y \oplus src1.y
1266 dst.z = src0.z \oplus src1.z
1268 dst.w = src0.w \oplus src1.w
1271 .. opcode:: IMAX - Maximum of Signed Integers
1275 dst.x = max(src0.x, src1.x)
1277 dst.y = max(src0.y, src1.y)
1279 dst.z = max(src0.z, src1.z)
1281 dst.w = max(src0.w, src1.w)
1284 .. opcode:: UMAX - Maximum of Unsigned Integers
1288 dst.x = max(src0.x, src1.x)
1290 dst.y = max(src0.y, src1.y)
1292 dst.z = max(src0.z, src1.z)
1294 dst.w = max(src0.w, src1.w)
1297 .. opcode:: IMIN - Minimum of Signed Integers
1301 dst.x = min(src0.x, src1.x)
1303 dst.y = min(src0.y, src1.y)
1305 dst.z = min(src0.z, src1.z)
1307 dst.w = min(src0.w, src1.w)
1310 .. opcode:: UMIN - Minimum of Unsigned Integers
1314 dst.x = min(src0.x, src1.x)
1316 dst.y = min(src0.y, src1.y)
1318 dst.z = min(src0.z, src1.z)
1320 dst.w = min(src0.w, src1.w)
1323 .. opcode:: SHL - Shift Left
1325 The shift count is masked with 0x1f before the shift is applied.
1329 dst.x = src0.x << (0x1f \& src1.x)
1331 dst.y = src0.y << (0x1f \& src1.y)
1333 dst.z = src0.z << (0x1f \& src1.z)
1335 dst.w = src0.w << (0x1f \& src1.w)
1338 .. opcode:: ISHR - Arithmetic Shift Right (of Signed Integer)
1340 The shift count is masked with 0x1f before the shift is applied.
1344 dst.x = src0.x >> (0x1f \& src1.x)
1346 dst.y = src0.y >> (0x1f \& src1.y)
1348 dst.z = src0.z >> (0x1f \& src1.z)
1350 dst.w = src0.w >> (0x1f \& src1.w)
1353 .. opcode:: USHR - Logical Shift Right
1355 The shift count is masked with 0x1f before the shift is applied.
1359 dst.x = src0.x >> (unsigned) (0x1f \& src1.x)
1361 dst.y = src0.y >> (unsigned) (0x1f \& src1.y)
1363 dst.z = src0.z >> (unsigned) (0x1f \& src1.z)
1365 dst.w = src0.w >> (unsigned) (0x1f \& src1.w)
1368 .. opcode:: UCMP - Integer Conditional Move
1372 dst.x = src0.x ? src1.x : src2.x
1374 dst.y = src0.y ? src1.y : src2.y
1376 dst.z = src0.z ? src1.z : src2.z
1378 dst.w = src0.w ? src1.w : src2.w
1382 .. opcode:: ISSG - Integer Set Sign
1386 dst.x = (src0.x < 0) ? -1 : (src0.x > 0) ? 1 : 0
1388 dst.y = (src0.y < 0) ? -1 : (src0.y > 0) ? 1 : 0
1390 dst.z = (src0.z < 0) ? -1 : (src0.z > 0) ? 1 : 0
1392 dst.w = (src0.w < 0) ? -1 : (src0.w > 0) ? 1 : 0
1396 .. opcode:: FSLT - Float Set On Less Than (ordered)
1398 Same comparison as SLT but returns integer instead of 1.0/0.0 float
1402 dst.x = (src0.x < src1.x) ? \sim 0 : 0
1404 dst.y = (src0.y < src1.y) ? \sim 0 : 0
1406 dst.z = (src0.z < src1.z) ? \sim 0 : 0
1408 dst.w = (src0.w < src1.w) ? \sim 0 : 0
1411 .. opcode:: ISLT - Signed Integer Set On Less Than
1415 dst.x = (src0.x < src1.x) ? \sim 0 : 0
1417 dst.y = (src0.y < src1.y) ? \sim 0 : 0
1419 dst.z = (src0.z < src1.z) ? \sim 0 : 0
1421 dst.w = (src0.w < src1.w) ? \sim 0 : 0
1424 .. opcode:: USLT - Unsigned Integer Set On Less Than
1428 dst.x = (src0.x < src1.x) ? \sim 0 : 0
1430 dst.y = (src0.y < src1.y) ? \sim 0 : 0
1432 dst.z = (src0.z < src1.z) ? \sim 0 : 0
1434 dst.w = (src0.w < src1.w) ? \sim 0 : 0
1437 .. opcode:: FSGE - Float Set On Greater Equal Than (ordered)
1439 Same comparison as SGE but returns integer instead of 1.0/0.0 float
1443 dst.x = (src0.x >= src1.x) ? \sim 0 : 0
1445 dst.y = (src0.y >= src1.y) ? \sim 0 : 0
1447 dst.z = (src0.z >= src1.z) ? \sim 0 : 0
1449 dst.w = (src0.w >= src1.w) ? \sim 0 : 0
1452 .. opcode:: ISGE - Signed Integer Set On Greater Equal Than
1456 dst.x = (src0.x >= src1.x) ? \sim 0 : 0
1458 dst.y = (src0.y >= src1.y) ? \sim 0 : 0
1460 dst.z = (src0.z >= src1.z) ? \sim 0 : 0
1462 dst.w = (src0.w >= src1.w) ? \sim 0 : 0
1465 .. opcode:: USGE - Unsigned Integer Set On Greater Equal Than
1469 dst.x = (src0.x >= src1.x) ? \sim 0 : 0
1471 dst.y = (src0.y >= src1.y) ? \sim 0 : 0
1473 dst.z = (src0.z >= src1.z) ? \sim 0 : 0
1475 dst.w = (src0.w >= src1.w) ? \sim 0 : 0
1478 .. opcode:: FSEQ - Float Set On Equal (ordered)
1480 Same comparison as SEQ but returns integer instead of 1.0/0.0 float
1484 dst.x = (src0.x == src1.x) ? \sim 0 : 0
1486 dst.y = (src0.y == src1.y) ? \sim 0 : 0
1488 dst.z = (src0.z == src1.z) ? \sim 0 : 0
1490 dst.w = (src0.w == src1.w) ? \sim 0 : 0
1493 .. opcode:: USEQ - Integer Set On Equal
1497 dst.x = (src0.x == src1.x) ? \sim 0 : 0
1499 dst.y = (src0.y == src1.y) ? \sim 0 : 0
1501 dst.z = (src0.z == src1.z) ? \sim 0 : 0
1503 dst.w = (src0.w == src1.w) ? \sim 0 : 0
1506 .. opcode:: FSNE - Float Set On Not Equal (unordered)
1508 Same comparison as SNE but returns integer instead of 1.0/0.0 float
1512 dst.x = (src0.x != src1.x) ? \sim 0 : 0
1514 dst.y = (src0.y != src1.y) ? \sim 0 : 0
1516 dst.z = (src0.z != src1.z) ? \sim 0 : 0
1518 dst.w = (src0.w != src1.w) ? \sim 0 : 0
1521 .. opcode:: USNE - Integer Set On Not Equal
1525 dst.x = (src0.x != src1.x) ? \sim 0 : 0
1527 dst.y = (src0.y != src1.y) ? \sim 0 : 0
1529 dst.z = (src0.z != src1.z) ? \sim 0 : 0
1531 dst.w = (src0.w != src1.w) ? \sim 0 : 0
1534 .. opcode:: INEG - Integer Negate
1549 .. opcode:: IABS - Integer Absolute Value
1563 These opcodes are used for bit-level manipulation of integers.
1565 .. opcode:: IBFE - Signed Bitfield Extract
1567 See SM5 instruction of the same name. Extracts a set of bits from the input,
1568 and sign-extends them if the high bit of the extracted window is set.
1572 def ibfe(value, offset, bits):
1573 offset = offset & 0x1f
1575 if bits == 0: return 0
1576 # Note: >> sign-extends
1577 if width + offset < 32:
1578 return (value << (32 - offset - bits)) >> (32 - bits)
1580 return value >> offset
1582 .. opcode:: UBFE - Unsigned Bitfield Extract
1584 See SM5 instruction of the same name. Extracts a set of bits from the input,
1585 without any sign-extension.
1589 def ubfe(value, offset, bits):
1590 offset = offset & 0x1f
1592 if bits == 0: return 0
1593 # Note: >> does not sign-extend
1594 if width + offset < 32:
1595 return (value << (32 - offset - bits)) >> (32 - bits)
1597 return value >> offset
1599 .. opcode:: BFI - Bitfield Insert
1601 See SM5 instruction of the same name. Replaces a bit region of 'base' with
1602 the low bits of 'insert'.
1606 def bfi(base, insert, offset, bits):
1607 offset = offset & 0x1f
1609 mask = ((1 << bits) - 1) << offset
1610 return ((insert << offset) & mask) | (base & ~mask)
1612 .. opcode:: BREV - Bitfield Reverse
1614 See SM5 instruction BFREV. Reverses the bits of the argument.
1616 .. opcode:: POPC - Population Count
1618 See SM5 instruction COUNTBITS. Counts the number of set bits in the argument.
1620 .. opcode:: LSB - Index of lowest set bit
1622 See SM5 instruction FIRSTBIT_LO. Computes the 0-based index of the first set
1623 bit of the argument. Returns -1 if none are set.
1625 .. opcode:: IMSB - Index of highest non-sign bit
1627 See SM5 instruction FIRSTBIT_SHI. Computes the 0-based index of the highest
1628 non-sign bit of the argument (i.e. highest 0 bit for negative numbers,
1629 highest 1 bit for positive numbers). Returns -1 if all bits are the same
1630 (i.e. for inputs 0 and -1).
1632 .. opcode:: UMSB - Index of highest set bit
1634 See SM5 instruction FIRSTBIT_HI. Computes the 0-based index of the highest
1635 set bit of the argument. Returns -1 if none are set.
1638 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1640 These opcodes are only supported in geometry shaders; they have no meaning
1641 in any other type of shader.
1643 .. opcode:: EMIT - Emit
1645 Generate a new vertex for the current primitive using the values in the
1649 .. opcode:: ENDPRIM - End Primitive
1651 Complete the current primitive (consisting of the emitted vertices),
1652 and start a new one.
1658 These opcodes are part of :term:`GLSL`'s opcode set. Support for these
1659 opcodes is determined by a special capability bit, ``GLSL``.
1660 Some require glsl version 1.30 (UIF/BREAKC/SWITCH/CASE/DEFAULT/ENDSWITCH).
1662 .. opcode:: CAL - Subroutine Call
1668 .. opcode:: RET - Subroutine Call Return
1673 .. opcode:: CONT - Continue
1675 Unconditionally moves the point of execution to the instruction after the
1676 last bgnloop. The instruction must appear within a bgnloop/endloop.
1680 Support for CONT is determined by a special capability bit,
1681 ``TGSI_CONT_SUPPORTED``. See :ref:`Screen` for more information.
1684 .. opcode:: BGNLOOP - Begin a Loop
1686 Start a loop. Must have a matching endloop.
1689 .. opcode:: BGNSUB - Begin Subroutine
1691 Starts definition of a subroutine. Must have a matching endsub.
1694 .. opcode:: ENDLOOP - End a Loop
1696 End a loop started with bgnloop.
1699 .. opcode:: ENDSUB - End Subroutine
1701 Ends definition of a subroutine.
1704 .. opcode:: NOP - No Operation
1709 .. opcode:: BRK - Break
1711 Unconditionally moves the point of execution to the instruction after the
1712 next endloop or endswitch. The instruction must appear within a loop/endloop
1713 or switch/endswitch.
1716 .. opcode:: BREAKC - Break Conditional
1718 Conditionally moves the point of execution to the instruction after the
1719 next endloop or endswitch. The instruction must appear within a loop/endloop
1720 or switch/endswitch.
1721 Condition evaluates to true if src0.x != 0 where src0.x is interpreted
1722 as an integer register.
1726 Considered for removal as it's quite inconsistent wrt other opcodes
1727 (could emulate with UIF/BRK/ENDIF).
1730 .. opcode:: IF - Float If
1732 Start an IF ... ELSE .. ENDIF block. Condition evaluates to true if
1736 where src0.x is interpreted as a floating point register.
1739 .. opcode:: UIF - Bitwise If
1741 Start an UIF ... ELSE .. ENDIF block. Condition evaluates to true if
1745 where src0.x is interpreted as an integer register.
1748 .. opcode:: ELSE - Else
1750 Starts an else block, after an IF or UIF statement.
1753 .. opcode:: ENDIF - End If
1755 Ends an IF or UIF block.
1758 .. opcode:: SWITCH - Switch
1760 Starts a C-style switch expression. The switch consists of one or multiple
1761 CASE statements, and at most one DEFAULT statement. Execution of a statement
1762 ends when a BRK is hit, but just like in C falling through to other cases
1763 without a break is allowed. Similarly, DEFAULT label is allowed anywhere not
1764 just as last statement, and fallthrough is allowed into/from it.
1765 CASE src arguments are evaluated at bit level against the SWITCH src argument.
1771 (some instructions here)
1774 (some instructions here)
1777 (some instructions here)
1782 .. opcode:: CASE - Switch case
1784 This represents a switch case label. The src arg must be an integer immediate.
1787 .. opcode:: DEFAULT - Switch default
1789 This represents the default case in the switch, which is taken if no other
1793 .. opcode:: ENDSWITCH - End of switch
1795 Ends a switch expression.
1798 .. opcode:: NRM4 - 4-component Vector Normalise
1800 This instruction replicates its result.
1804 dst = \frac{src.x}{src.x \times src.x + src.y \times src.y + src.z \times src.z + src.w \times src.w}
1812 The double-precision opcodes reinterpret four-component vectors into
1813 two-component vectors with doubled precision in each component.
1815 Support for these opcodes is XXX undecided. :T
1817 .. opcode:: DADD - Add
1821 dst.xy = src0.xy + src1.xy
1823 dst.zw = src0.zw + src1.zw
1826 .. opcode:: DDIV - Divide
1830 dst.xy = src0.xy / src1.xy
1832 dst.zw = src0.zw / src1.zw
1834 .. opcode:: DSEQ - Set on Equal
1838 dst.xy = src0.xy == src1.xy ? 1.0F : 0.0F
1840 dst.zw = src0.zw == src1.zw ? 1.0F : 0.0F
1842 .. opcode:: DSLT - Set on Less than
1846 dst.xy = src0.xy < src1.xy ? 1.0F : 0.0F
1848 dst.zw = src0.zw < src1.zw ? 1.0F : 0.0F
1850 .. opcode:: DFRAC - Fraction
1854 dst.xy = src.xy - \lfloor src.xy\rfloor
1856 dst.zw = src.zw - \lfloor src.zw\rfloor
1859 .. opcode:: DFRACEXP - Convert Number to Fractional and Integral Components
1861 Like the ``frexp()`` routine in many math libraries, this opcode stores the
1862 exponent of its source to ``dst0``, and the significand to ``dst1``, such that
1863 :math:`dst1 \times 2^{dst0} = src` .
1867 dst0.xy = exp(src.xy)
1869 dst1.xy = frac(src.xy)
1871 dst0.zw = exp(src.zw)
1873 dst1.zw = frac(src.zw)
1875 .. opcode:: DLDEXP - Multiply Number by Integral Power of 2
1877 This opcode is the inverse of :opcode:`DFRACEXP`.
1881 dst.xy = src0.xy \times 2^{src1.xy}
1883 dst.zw = src0.zw \times 2^{src1.zw}
1885 .. opcode:: DMIN - Minimum
1889 dst.xy = min(src0.xy, src1.xy)
1891 dst.zw = min(src0.zw, src1.zw)
1893 .. opcode:: DMAX - Maximum
1897 dst.xy = max(src0.xy, src1.xy)
1899 dst.zw = max(src0.zw, src1.zw)
1901 .. opcode:: DMUL - Multiply
1905 dst.xy = src0.xy \times src1.xy
1907 dst.zw = src0.zw \times src1.zw
1910 .. opcode:: DMAD - Multiply And Add
1914 dst.xy = src0.xy \times src1.xy + src2.xy
1916 dst.zw = src0.zw \times src1.zw + src2.zw
1919 .. opcode:: DRCP - Reciprocal
1923 dst.xy = \frac{1}{src.xy}
1925 dst.zw = \frac{1}{src.zw}
1927 .. opcode:: DSQRT - Square Root
1931 dst.xy = \sqrt{src.xy}
1933 dst.zw = \sqrt{src.zw}
1936 .. _samplingopcodes:
1938 Resource Sampling Opcodes
1939 ^^^^^^^^^^^^^^^^^^^^^^^^^
1941 Those opcodes follow very closely semantics of the respective Direct3D
1942 instructions. If in doubt double check Direct3D documentation.
1943 Note that the swizzle on SVIEW (src1) determines texel swizzling
1948 Using provided address, sample data from the specified texture using the
1949 filtering mode identified by the gven sampler. The source data may come from
1950 any resource type other than buffers.
1952 Syntax: ``SAMPLE dst, address, sampler_view, sampler``
1954 Example: ``SAMPLE TEMP[0], TEMP[1], SVIEW[0], SAMP[0]``
1956 .. opcode:: SAMPLE_I
1958 Simplified alternative to the SAMPLE instruction. Using the provided
1959 integer address, SAMPLE_I fetches data from the specified sampler view
1960 without any filtering. The source data may come from any resource type
1963 Syntax: ``SAMPLE_I dst, address, sampler_view``
1965 Example: ``SAMPLE_I TEMP[0], TEMP[1], SVIEW[0]``
1967 The 'address' is specified as unsigned integers. If the 'address' is out of
1968 range [0...(# texels - 1)] the result of the fetch is always 0 in all
1969 components. As such the instruction doesn't honor address wrap modes, in
1970 cases where that behavior is desirable 'SAMPLE' instruction should be used.
1971 address.w always provides an unsigned integer mipmap level. If the value is
1972 out of the range then the instruction always returns 0 in all components.
1973 address.yz are ignored for buffers and 1d textures. address.z is ignored
1974 for 1d texture arrays and 2d textures.
1976 For 1D texture arrays address.y provides the array index (also as unsigned
1977 integer). If the value is out of the range of available array indices
1978 [0... (array size - 1)] then the opcode always returns 0 in all components.
1979 For 2D texture arrays address.z provides the array index, otherwise it
1980 exhibits the same behavior as in the case for 1D texture arrays. The exact
1981 semantics of the source address are presented in the table below:
1983 +---------------------------+----+-----+-----+---------+
1984 | resource type | X | Y | Z | W |
1985 +===========================+====+=====+=====+=========+
1986 | ``PIPE_BUFFER`` | x | | | ignored |
1987 +---------------------------+----+-----+-----+---------+
1988 | ``PIPE_TEXTURE_1D`` | x | | | mpl |
1989 +---------------------------+----+-----+-----+---------+
1990 | ``PIPE_TEXTURE_2D`` | x | y | | mpl |
1991 +---------------------------+----+-----+-----+---------+
1992 | ``PIPE_TEXTURE_3D`` | x | y | z | mpl |
1993 +---------------------------+----+-----+-----+---------+
1994 | ``PIPE_TEXTURE_RECT`` | x | y | | mpl |
1995 +---------------------------+----+-----+-----+---------+
1996 | ``PIPE_TEXTURE_CUBE`` | not allowed as source |
1997 +---------------------------+----+-----+-----+---------+
1998 | ``PIPE_TEXTURE_1D_ARRAY`` | x | idx | | mpl |
1999 +---------------------------+----+-----+-----+---------+
2000 | ``PIPE_TEXTURE_2D_ARRAY`` | x | y | idx | mpl |
2001 +---------------------------+----+-----+-----+---------+
2003 Where 'mpl' is a mipmap level and 'idx' is the array index.
2005 .. opcode:: SAMPLE_I_MS
2007 Just like SAMPLE_I but allows fetch data from multi-sampled surfaces.
2009 Syntax: ``SAMPLE_I_MS dst, address, sampler_view, sample``
2011 .. opcode:: SAMPLE_B
2013 Just like the SAMPLE instruction with the exception that an additional bias
2014 is applied to the level of detail computed as part of the instruction
2017 Syntax: ``SAMPLE_B dst, address, sampler_view, sampler, lod_bias``
2019 Example: ``SAMPLE_B TEMP[0], TEMP[1], SVIEW[0], SAMP[0], TEMP[2].x``
2021 .. opcode:: SAMPLE_C
2023 Similar to the SAMPLE instruction but it performs a comparison filter. The
2024 operands to SAMPLE_C are identical to SAMPLE, except that there is an
2025 additional float32 operand, reference value, which must be a register with
2026 single-component, or a scalar literal. SAMPLE_C makes the hardware use the
2027 current samplers compare_func (in pipe_sampler_state) to compare reference
2028 value against the red component value for the surce resource at each texel
2029 that the currently configured texture filter covers based on the provided
2032 Syntax: ``SAMPLE_C dst, address, sampler_view.r, sampler, ref_value``
2034 Example: ``SAMPLE_C TEMP[0], TEMP[1], SVIEW[0].r, SAMP[0], TEMP[2].x``
2036 .. opcode:: SAMPLE_C_LZ
2038 Same as SAMPLE_C, but LOD is 0 and derivatives are ignored. The LZ stands
2041 Syntax: ``SAMPLE_C_LZ dst, address, sampler_view.r, sampler, ref_value``
2043 Example: ``SAMPLE_C_LZ TEMP[0], TEMP[1], SVIEW[0].r, SAMP[0], TEMP[2].x``
2046 .. opcode:: SAMPLE_D
2048 SAMPLE_D is identical to the SAMPLE opcode except that the derivatives for
2049 the source address in the x direction and the y direction are provided by
2052 Syntax: ``SAMPLE_D dst, address, sampler_view, sampler, der_x, der_y``
2054 Example: ``SAMPLE_D TEMP[0], TEMP[1], SVIEW[0], SAMP[0], TEMP[2], TEMP[3]``
2056 .. opcode:: SAMPLE_L
2058 SAMPLE_L is identical to the SAMPLE opcode except that the LOD is provided
2059 directly as a scalar value, representing no anisotropy.
2061 Syntax: ``SAMPLE_L dst, address, sampler_view, sampler, explicit_lod``
2063 Example: ``SAMPLE_L TEMP[0], TEMP[1], SVIEW[0], SAMP[0], TEMP[2].x``
2067 Gathers the four texels to be used in a bi-linear filtering operation and
2068 packs them into a single register. Only works with 2D, 2D array, cubemaps,
2069 and cubemaps arrays. For 2D textures, only the addressing modes of the
2070 sampler and the top level of any mip pyramid are used. Set W to zero. It
2071 behaves like the SAMPLE instruction, but a filtered sample is not
2072 generated. The four samples that contribute to filtering are placed into
2073 xyzw in counter-clockwise order, starting with the (u,v) texture coordinate
2074 delta at the following locations (-, +), (+, +), (+, -), (-, -), where the
2075 magnitude of the deltas are half a texel.
2078 .. opcode:: SVIEWINFO
2080 Query the dimensions of a given sampler view. dst receives width, height,
2081 depth or array size and number of mipmap levels as int4. The dst can have a
2082 writemask which will specify what info is the caller interested in.
2084 Syntax: ``SVIEWINFO dst, src_mip_level, sampler_view``
2086 Example: ``SVIEWINFO TEMP[0], TEMP[1].x, SVIEW[0]``
2088 src_mip_level is an unsigned integer scalar. If it's out of range then
2089 returns 0 for width, height and depth/array size but the total number of
2090 mipmap is still returned correctly for the given sampler view. The returned
2091 width, height and depth values are for the mipmap level selected by the
2092 src_mip_level and are in the number of texels. For 1d texture array width
2093 is in dst.x, array size is in dst.y and dst.z is 0. The number of mipmaps is
2094 still in dst.w. In contrast to d3d10 resinfo, there's no way in the tgsi
2095 instruction encoding to specify the return type (float/rcpfloat/uint), hence
2096 always using uint. Also, unlike the SAMPLE instructions, the swizzle on src1
2097 resinfo allowing swizzling dst values is ignored (due to the interaction
2098 with rcpfloat modifier which requires some swizzle handling in the state
2101 .. opcode:: SAMPLE_POS
2103 Query the position of a given sample. dst receives float4 (x, y, 0, 0)
2104 indicated where the sample is located. If the resource is not a multi-sample
2105 resource and not a render target, the result is 0.
2107 .. opcode:: SAMPLE_INFO
2109 dst receives number of samples in x. If the resource is not a multi-sample
2110 resource and not a render target, the result is 0.
2113 .. _resourceopcodes:
2115 Resource Access Opcodes
2116 ^^^^^^^^^^^^^^^^^^^^^^^
2118 .. opcode:: LOAD - Fetch data from a shader resource
2120 Syntax: ``LOAD dst, resource, address``
2122 Example: ``LOAD TEMP[0], RES[0], TEMP[1]``
2124 Using the provided integer address, LOAD fetches data
2125 from the specified buffer or texture without any
2128 The 'address' is specified as a vector of unsigned
2129 integers. If the 'address' is out of range the result
2132 Only the first mipmap level of a resource can be read
2133 from using this instruction.
2135 For 1D or 2D texture arrays, the array index is
2136 provided as an unsigned integer in address.y or
2137 address.z, respectively. address.yz are ignored for
2138 buffers and 1D textures. address.z is ignored for 1D
2139 texture arrays and 2D textures. address.w is always
2142 .. opcode:: STORE - Write data to a shader resource
2144 Syntax: ``STORE resource, address, src``
2146 Example: ``STORE RES[0], TEMP[0], TEMP[1]``
2148 Using the provided integer address, STORE writes data
2149 to the specified buffer or texture.
2151 The 'address' is specified as a vector of unsigned
2152 integers. If the 'address' is out of range the result
2155 Only the first mipmap level of a resource can be
2156 written to using this instruction.
2158 For 1D or 2D texture arrays, the array index is
2159 provided as an unsigned integer in address.y or
2160 address.z, respectively. address.yz are ignored for
2161 buffers and 1D textures. address.z is ignored for 1D
2162 texture arrays and 2D textures. address.w is always
2166 .. _threadsyncopcodes:
2168 Inter-thread synchronization opcodes
2169 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2171 These opcodes are intended for communication between threads running
2172 within the same compute grid. For now they're only valid in compute
2175 .. opcode:: MFENCE - Memory fence
2177 Syntax: ``MFENCE resource``
2179 Example: ``MFENCE RES[0]``
2181 This opcode forces strong ordering between any memory access
2182 operations that affect the specified resource. This means that
2183 previous loads and stores (and only those) will be performed and
2184 visible to other threads before the program execution continues.
2187 .. opcode:: LFENCE - Load memory fence
2189 Syntax: ``LFENCE resource``
2191 Example: ``LFENCE RES[0]``
2193 Similar to MFENCE, but it only affects the ordering of memory loads.
2196 .. opcode:: SFENCE - Store memory fence
2198 Syntax: ``SFENCE resource``
2200 Example: ``SFENCE RES[0]``
2202 Similar to MFENCE, but it only affects the ordering of memory stores.
2205 .. opcode:: BARRIER - Thread group barrier
2209 This opcode suspends the execution of the current thread until all
2210 the remaining threads in the working group reach the same point of
2211 the program. Results are unspecified if any of the remaining
2212 threads terminates or never reaches an executed BARRIER instruction.
2220 These opcodes provide atomic variants of some common arithmetic and
2221 logical operations. In this context atomicity means that another
2222 concurrent memory access operation that affects the same memory
2223 location is guaranteed to be performed strictly before or after the
2224 entire execution of the atomic operation.
2226 For the moment they're only valid in compute programs.
2228 .. opcode:: ATOMUADD - Atomic integer addition
2230 Syntax: ``ATOMUADD dst, resource, offset, src``
2232 Example: ``ATOMUADD TEMP[0], RES[0], TEMP[1], TEMP[2]``
2234 The following operation is performed atomically on each component:
2238 dst_i = resource[offset]_i
2240 resource[offset]_i = dst_i + src_i
2243 .. opcode:: ATOMXCHG - Atomic exchange
2245 Syntax: ``ATOMXCHG dst, resource, offset, src``
2247 Example: ``ATOMXCHG TEMP[0], RES[0], TEMP[1], TEMP[2]``
2249 The following operation is performed atomically on each component:
2253 dst_i = resource[offset]_i
2255 resource[offset]_i = src_i
2258 .. opcode:: ATOMCAS - Atomic compare-and-exchange
2260 Syntax: ``ATOMCAS dst, resource, offset, cmp, src``
2262 Example: ``ATOMCAS TEMP[0], RES[0], TEMP[1], TEMP[2], TEMP[3]``
2264 The following operation is performed atomically on each component:
2268 dst_i = resource[offset]_i
2270 resource[offset]_i = (dst_i == cmp_i ? src_i : dst_i)
2273 .. opcode:: ATOMAND - Atomic bitwise And
2275 Syntax: ``ATOMAND dst, resource, offset, src``
2277 Example: ``ATOMAND TEMP[0], RES[0], TEMP[1], TEMP[2]``
2279 The following operation is performed atomically on each component:
2283 dst_i = resource[offset]_i
2285 resource[offset]_i = dst_i \& src_i
2288 .. opcode:: ATOMOR - Atomic bitwise Or
2290 Syntax: ``ATOMOR dst, resource, offset, src``
2292 Example: ``ATOMOR TEMP[0], RES[0], TEMP[1], TEMP[2]``
2294 The following operation is performed atomically on each component:
2298 dst_i = resource[offset]_i
2300 resource[offset]_i = dst_i | src_i
2303 .. opcode:: ATOMXOR - Atomic bitwise Xor
2305 Syntax: ``ATOMXOR dst, resource, offset, src``
2307 Example: ``ATOMXOR TEMP[0], RES[0], TEMP[1], TEMP[2]``
2309 The following operation is performed atomically on each component:
2313 dst_i = resource[offset]_i
2315 resource[offset]_i = dst_i \oplus src_i
2318 .. opcode:: ATOMUMIN - Atomic unsigned minimum
2320 Syntax: ``ATOMUMIN dst, resource, offset, src``
2322 Example: ``ATOMUMIN TEMP[0], RES[0], TEMP[1], TEMP[2]``
2324 The following operation is performed atomically on each component:
2328 dst_i = resource[offset]_i
2330 resource[offset]_i = (dst_i < src_i ? dst_i : src_i)
2333 .. opcode:: ATOMUMAX - Atomic unsigned maximum
2335 Syntax: ``ATOMUMAX dst, resource, offset, src``
2337 Example: ``ATOMUMAX TEMP[0], RES[0], TEMP[1], TEMP[2]``
2339 The following operation is performed atomically on each component:
2343 dst_i = resource[offset]_i
2345 resource[offset]_i = (dst_i > src_i ? dst_i : src_i)
2348 .. opcode:: ATOMIMIN - Atomic signed minimum
2350 Syntax: ``ATOMIMIN dst, resource, offset, src``
2352 Example: ``ATOMIMIN TEMP[0], RES[0], TEMP[1], TEMP[2]``
2354 The following operation is performed atomically on each component:
2358 dst_i = resource[offset]_i
2360 resource[offset]_i = (dst_i < src_i ? dst_i : src_i)
2363 .. opcode:: ATOMIMAX - Atomic signed maximum
2365 Syntax: ``ATOMIMAX dst, resource, offset, src``
2367 Example: ``ATOMIMAX TEMP[0], RES[0], TEMP[1], TEMP[2]``
2369 The following operation is performed atomically on each component:
2373 dst_i = resource[offset]_i
2375 resource[offset]_i = (dst_i > src_i ? dst_i : src_i)
2379 Explanation of symbols used
2380 ------------------------------
2387 :math:`|x|` Absolute value of `x`.
2389 :math:`\lceil x \rceil` Ceiling of `x`.
2391 clamp(x,y,z) Clamp x between y and z.
2392 (x < y) ? y : (x > z) ? z : x
2394 :math:`\lfloor x\rfloor` Floor of `x`.
2396 :math:`\log_2{x}` Logarithm of `x`, base 2.
2398 max(x,y) Maximum of x and y.
2401 min(x,y) Minimum of x and y.
2404 partialx(x) Derivative of x relative to fragment's X.
2406 partialy(x) Derivative of x relative to fragment's Y.
2408 pop() Pop from stack.
2410 :math:`x^y` `x` to the power `y`.
2412 push(x) Push x on stack.
2416 trunc(x) Truncate x, i.e. drop the fraction bits.
2423 discard Discard fragment.
2427 target Label of target instruction.
2438 Declares a register that is will be referenced as an operand in Instruction
2441 File field contains register file that is being declared and is one
2444 UsageMask field specifies which of the register components can be accessed
2445 and is one of TGSI_WRITEMASK.
2447 The Local flag specifies that a given value isn't intended for
2448 subroutine parameter passing and, as a result, the implementation
2449 isn't required to give any guarantees of it being preserved across
2450 subroutine boundaries. As it's merely a compiler hint, the
2451 implementation is free to ignore it.
2453 If Dimension flag is set to 1, a Declaration Dimension token follows.
2455 If Semantic flag is set to 1, a Declaration Semantic token follows.
2457 If Interpolate flag is set to 1, a Declaration Interpolate token follows.
2459 If file is TGSI_FILE_RESOURCE, a Declaration Resource token follows.
2461 If Array flag is set to 1, a Declaration Array token follows.
2464 ^^^^^^^^^^^^^^^^^^^^^^^^
2466 Declarations can optional have an ArrayID attribute which can be referred by
2467 indirect addressing operands. An ArrayID of zero is reserved and treaded as
2468 if no ArrayID is specified.
2470 If an indirect addressing operand refers to a specific declaration by using
2471 an ArrayID only the registers in this declaration are guaranteed to be
2472 accessed, accessing any register outside this declaration results in undefined
2473 behavior. Note that for compatibility the effective index is zero-based and
2474 not relative to the specified declaration
2476 If no ArrayID is specified with an indirect addressing operand the whole
2477 register file might be accessed by this operand. This is strongly discouraged
2478 and will prevent packing of scalar/vec2 arrays and effective alias analysis.
2480 Declaration Semantic
2481 ^^^^^^^^^^^^^^^^^^^^^^^^
2483 Vertex and fragment shader input and output registers may be labeled
2484 with semantic information consisting of a name and index.
2486 Follows Declaration token if Semantic bit is set.
2488 Since its purpose is to link a shader with other stages of the pipeline,
2489 it is valid to follow only those Declaration tokens that declare a register
2490 either in INPUT or OUTPUT file.
2492 SemanticName field contains the semantic name of the register being declared.
2493 There is no default value.
2495 SemanticIndex is an optional subscript that can be used to distinguish
2496 different register declarations with the same semantic name. The default value
2499 The meanings of the individual semantic names are explained in the following
2502 TGSI_SEMANTIC_POSITION
2503 """"""""""""""""""""""
2505 For vertex shaders, TGSI_SEMANTIC_POSITION indicates the vertex shader
2506 output register which contains the homogeneous vertex position in the clip
2507 space coordinate system. After clipping, the X, Y and Z components of the
2508 vertex will be divided by the W value to get normalized device coordinates.
2510 For fragment shaders, TGSI_SEMANTIC_POSITION is used to indicate that
2511 fragment shader input contains the fragment's window position. The X
2512 component starts at zero and always increases from left to right.
2513 The Y component starts at zero and always increases but Y=0 may either
2514 indicate the top of the window or the bottom depending on the fragment
2515 coordinate origin convention (see TGSI_PROPERTY_FS_COORD_ORIGIN).
2516 The Z coordinate ranges from 0 to 1 to represent depth from the front
2517 to the back of the Z buffer. The W component contains the reciprocol
2518 of the interpolated vertex position W component.
2520 Fragment shaders may also declare an output register with
2521 TGSI_SEMANTIC_POSITION. Only the Z component is writable. This allows
2522 the fragment shader to change the fragment's Z position.
2529 For vertex shader outputs or fragment shader inputs/outputs, this
2530 label indicates that the resister contains an R,G,B,A color.
2532 Several shader inputs/outputs may contain colors so the semantic index
2533 is used to distinguish them. For example, color[0] may be the diffuse
2534 color while color[1] may be the specular color.
2536 This label is needed so that the flat/smooth shading can be applied
2537 to the right interpolants during rasterization.
2541 TGSI_SEMANTIC_BCOLOR
2542 """"""""""""""""""""
2544 Back-facing colors are only used for back-facing polygons, and are only valid
2545 in vertex shader outputs. After rasterization, all polygons are front-facing
2546 and COLOR and BCOLOR end up occupying the same slots in the fragment shader,
2547 so all BCOLORs effectively become regular COLORs in the fragment shader.
2553 Vertex shader inputs and outputs and fragment shader inputs may be
2554 labeled with TGSI_SEMANTIC_FOG to indicate that the register contains
2555 a fog coordinate. Typically, the fragment shader will use the fog coordinate
2556 to compute a fog blend factor which is used to blend the normal fragment color
2557 with a constant fog color. But fog coord really is just an ordinary vec4
2558 register like regular semantics.
2564 Vertex shader input and output registers may be labeled with
2565 TGIS_SEMANTIC_PSIZE to indicate that the register contains a point size
2566 in the form (S, 0, 0, 1). The point size controls the width or diameter
2567 of points for rasterization. This label cannot be used in fragment
2570 When using this semantic, be sure to set the appropriate state in the
2571 :ref:`rasterizer` first.
2574 TGSI_SEMANTIC_TEXCOORD
2575 """"""""""""""""""""""
2577 Only available if PIPE_CAP_TGSI_TEXCOORD is exposed !
2579 Vertex shader outputs and fragment shader inputs may be labeled with
2580 this semantic to make them replaceable by sprite coordinates via the
2581 sprite_coord_enable state in the :ref:`rasterizer`.
2582 The semantic index permitted with this semantic is limited to <= 7.
2584 If the driver does not support TEXCOORD, sprite coordinate replacement
2585 applies to inputs with the GENERIC semantic instead.
2587 The intended use case for this semantic is gl_TexCoord.
2590 TGSI_SEMANTIC_PCOORD
2591 """"""""""""""""""""
2593 Only available if PIPE_CAP_TGSI_TEXCOORD is exposed !
2595 Fragment shader inputs may be labeled with TGSI_SEMANTIC_PCOORD to indicate
2596 that the register contains sprite coordinates in the form (x, y, 0, 1), if
2597 the current primitive is a point and point sprites are enabled. Otherwise,
2598 the contents of the register are undefined.
2600 The intended use case for this semantic is gl_PointCoord.
2603 TGSI_SEMANTIC_GENERIC
2604 """""""""""""""""""""
2606 All vertex/fragment shader inputs/outputs not labeled with any other
2607 semantic label can be considered to be generic attributes. Typical
2608 uses of generic inputs/outputs are texcoords and user-defined values.
2611 TGSI_SEMANTIC_NORMAL
2612 """"""""""""""""""""
2614 Indicates that a vertex shader input is a normal vector. This is
2615 typically only used for legacy graphics APIs.
2621 This label applies to fragment shader inputs only and indicates that
2622 the register contains front/back-face information of the form (F, 0,
2623 0, 1). The first component will be positive when the fragment belongs
2624 to a front-facing polygon, and negative when the fragment belongs to a
2625 back-facing polygon.
2628 TGSI_SEMANTIC_EDGEFLAG
2629 """"""""""""""""""""""
2631 For vertex shaders, this sematic label indicates that an input or
2632 output is a boolean edge flag. The register layout is [F, x, x, x]
2633 where F is 0.0 or 1.0 and x = don't care. Normally, the vertex shader
2634 simply copies the edge flag input to the edgeflag output.
2636 Edge flags are used to control which lines or points are actually
2637 drawn when the polygon mode converts triangles/quads/polygons into
2641 TGSI_SEMANTIC_STENCIL
2642 """""""""""""""""""""
2644 For fragment shaders, this semantic label indicates that an output
2645 is a writable stencil reference value. Only the Y component is writable.
2646 This allows the fragment shader to change the fragments stencilref value.
2649 TGSI_SEMANTIC_VIEWPORT_INDEX
2650 """"""""""""""""""""""""""""
2652 For geometry shaders, this semantic label indicates that an output
2653 contains the index of the viewport (and scissor) to use.
2654 Only the X value is used.
2660 For geometry shaders, this semantic label indicates that an output
2661 contains the layer value to use for the color and depth/stencil surfaces.
2662 Only the X value is used. (Also known as rendertarget array index.)
2665 TGSI_SEMANTIC_CULLDIST
2666 """"""""""""""""""""""
2668 Used as distance to plane for performing application-defined culling
2669 of individual primitives against a plane. When components of vertex
2670 elements are given this label, these values are assumed to be a
2671 float32 signed distance to a plane. Primitives will be completely
2672 discarded if the plane distance for all of the vertices in the
2673 primitive are < 0. If a vertex has a cull distance of NaN, that
2674 vertex counts as "out" (as if its < 0);
2675 The limits on both clip and cull distances are bound
2676 by the PIPE_MAX_CLIP_OR_CULL_DISTANCE_COUNT define which defines
2677 the maximum number of components that can be used to hold the
2678 distances and by the PIPE_MAX_CLIP_OR_CULL_DISTANCE_ELEMENT_COUNT
2679 which specifies the maximum number of registers which can be
2680 annotated with those semantics.
2683 TGSI_SEMANTIC_CLIPDIST
2684 """"""""""""""""""""""
2686 When components of vertex elements are identified this way, these
2687 values are each assumed to be a float32 signed distance to a plane.
2688 Primitive setup only invokes rasterization on pixels for which
2689 the interpolated plane distances are >= 0. Multiple clip planes
2690 can be implemented simultaneously, by annotating multiple
2691 components of one or more vertex elements with the above specified
2692 semantic. The limits on both clip and cull distances are bound
2693 by the PIPE_MAX_CLIP_OR_CULL_DISTANCE_COUNT define which defines
2694 the maximum number of components that can be used to hold the
2695 distances and by the PIPE_MAX_CLIP_OR_CULL_DISTANCE_ELEMENT_COUNT
2696 which specifies the maximum number of registers which can be
2697 annotated with those semantics.
2699 TGSI_SEMANTIC_SAMPLEID
2700 """"""""""""""""""""""
2702 For fragment shaders, this semantic label indicates that a system value
2703 contains the current sample id (i.e. gl_SampleID). Only the X value is used.
2705 TGSI_SEMANTIC_SAMPLEPOS
2706 """""""""""""""""""""""
2708 For fragment shaders, this semantic label indicates that a system value
2709 contains the current sample's position (i.e. gl_SamplePosition). Only the X
2710 and Y values are used.
2712 TGSI_SEMANTIC_SAMPLEMASK
2713 """"""""""""""""""""""""
2715 For fragment shaders, this semantic label indicates that an output contains
2716 the sample mask used to disable further sample processing
2717 (i.e. gl_SampleMask). Only the X value is used, up to 32x MS.
2719 TGSI_SEMANTIC_INVOCATIONID
2720 """"""""""""""""""""""""""
2722 For geometry shaders, this semantic label indicates that a system value
2723 contains the current invocation id (i.e. gl_InvocationID). Only the X value is
2726 Declaration Interpolate
2727 ^^^^^^^^^^^^^^^^^^^^^^^
2729 This token is only valid for fragment shader INPUT declarations.
2731 The Interpolate field specifes the way input is being interpolated by
2732 the rasteriser and is one of TGSI_INTERPOLATE_*.
2734 The CylindricalWrap bitfield specifies which register components
2735 should be subject to cylindrical wrapping when interpolating by the
2736 rasteriser. If TGSI_CYLINDRICAL_WRAP_X is set to 1, the X component
2737 should be interpolated according to cylindrical wrapping rules.
2740 Declaration Sampler View
2741 ^^^^^^^^^^^^^^^^^^^^^^^^
2743 Follows Declaration token if file is TGSI_FILE_SAMPLER_VIEW.
2745 DCL SVIEW[#], resource, type(s)
2747 Declares a shader input sampler view and assigns it to a SVIEW[#]
2750 resource can be one of BUFFER, 1D, 2D, 3D, 1DArray and 2DArray.
2752 type must be 1 or 4 entries (if specifying on a per-component
2753 level) out of UNORM, SNORM, SINT, UINT and FLOAT.
2756 Declaration Resource
2757 ^^^^^^^^^^^^^^^^^^^^
2759 Follows Declaration token if file is TGSI_FILE_RESOURCE.
2761 DCL RES[#], resource [, WR] [, RAW]
2763 Declares a shader input resource and assigns it to a RES[#]
2766 resource can be one of BUFFER, 1D, 2D, 3D, CUBE, 1DArray and
2769 If the RAW keyword is not specified, the texture data will be
2770 subject to conversion, swizzling and scaling as required to yield
2771 the specified data type from the physical data format of the bound
2774 If the RAW keyword is specified, no channel conversion will be
2775 performed: the values read for each of the channels (X,Y,Z,W) will
2776 correspond to consecutive words in the same order and format
2777 they're found in memory. No element-to-address conversion will be
2778 performed either: the value of the provided X coordinate will be
2779 interpreted in byte units instead of texel units. The result of
2780 accessing a misaligned address is undefined.
2782 Usage of the STORE opcode is only allowed if the WR (writable) flag
2787 ^^^^^^^^^^^^^^^^^^^^^^^^
2789 Properties are general directives that apply to the whole TGSI program.
2794 Specifies the fragment shader TGSI_SEMANTIC_POSITION coordinate origin.
2795 The default value is UPPER_LEFT.
2797 If UPPER_LEFT, the position will be (0,0) at the upper left corner and
2798 increase downward and rightward.
2799 If LOWER_LEFT, the position will be (0,0) at the lower left corner and
2800 increase upward and rightward.
2802 OpenGL defaults to LOWER_LEFT, and is configurable with the
2803 GL_ARB_fragment_coord_conventions extension.
2805 DirectX 9/10 use UPPER_LEFT.
2807 FS_COORD_PIXEL_CENTER
2808 """""""""""""""""""""
2810 Specifies the fragment shader TGSI_SEMANTIC_POSITION pixel center convention.
2811 The default value is HALF_INTEGER.
2813 If HALF_INTEGER, the fractionary part of the position will be 0.5
2814 If INTEGER, the fractionary part of the position will be 0.0
2816 Note that this does not affect the set of fragments generated by
2817 rasterization, which is instead controlled by half_pixel_center in the
2820 OpenGL defaults to HALF_INTEGER, and is configurable with the
2821 GL_ARB_fragment_coord_conventions extension.
2823 DirectX 9 uses INTEGER.
2824 DirectX 10 uses HALF_INTEGER.
2826 FS_COLOR0_WRITES_ALL_CBUFS
2827 """"""""""""""""""""""""""
2828 Specifies that writes to the fragment shader color 0 are replicated to all
2829 bound cbufs. This facilitates OpenGL's fragColor output vs fragData[0] where
2830 fragData is directed to a single color buffer, but fragColor is broadcast.
2833 """"""""""""""""""""""""""
2834 If this property is set on the program bound to the shader stage before the
2835 fragment shader, user clip planes should have no effect (be disabled) even if
2836 that shader does not write to any clip distance outputs and the rasterizer's
2837 clip_plane_enable is non-zero.
2838 This property is only supported by drivers that also support shader clip
2840 This is useful for APIs that don't have UCPs and where clip distances written
2841 by a shader cannot be disabled.
2846 Specifies the number of times a geometry shader should be executed for each
2847 input primitive. Each invocation will have a different
2848 TGSI_SEMANTIC_INVOCATIONID system value set. If not specified, assumed to
2851 VS_WINDOW_SPACE_POSITION
2852 """"""""""""""""""""""""""
2853 If this property is set on the vertex shader, the TGSI_SEMANTIC_POSITION output
2854 is assumed to contain window space coordinates.
2855 Division of X,Y,Z by W and the viewport transformation are disabled, and 1/W is
2856 directly taken from the 4-th component of the shader output.
2857 Naturally, clipping is not performed on window coordinates either.
2858 The effect of this property is undefined if a geometry or tessellation shader
2861 Texture Sampling and Texture Formats
2862 ------------------------------------
2864 This table shows how texture image components are returned as (x,y,z,w) tuples
2865 by TGSI texture instructions, such as :opcode:`TEX`, :opcode:`TXD`, and
2866 :opcode:`TXP`. For reference, OpenGL and Direct3D conventions are shown as
2869 +--------------------+--------------+--------------------+--------------+
2870 | Texture Components | Gallium | OpenGL | Direct3D 9 |
2871 +====================+==============+====================+==============+
2872 | R | (r, 0, 0, 1) | (r, 0, 0, 1) | (r, 1, 1, 1) |
2873 +--------------------+--------------+--------------------+--------------+
2874 | RG | (r, g, 0, 1) | (r, g, 0, 1) | (r, g, 1, 1) |
2875 +--------------------+--------------+--------------------+--------------+
2876 | RGB | (r, g, b, 1) | (r, g, b, 1) | (r, g, b, 1) |
2877 +--------------------+--------------+--------------------+--------------+
2878 | RGBA | (r, g, b, a) | (r, g, b, a) | (r, g, b, a) |
2879 +--------------------+--------------+--------------------+--------------+
2880 | A | (0, 0, 0, a) | (0, 0, 0, a) | (0, 0, 0, a) |
2881 +--------------------+--------------+--------------------+--------------+
2882 | L | (l, l, l, 1) | (l, l, l, 1) | (l, l, l, 1) |
2883 +--------------------+--------------+--------------------+--------------+
2884 | LA | (l, l, l, a) | (l, l, l, a) | (l, l, l, a) |
2885 +--------------------+--------------+--------------------+--------------+
2886 | I | (i, i, i, i) | (i, i, i, i) | N/A |
2887 +--------------------+--------------+--------------------+--------------+
2888 | UV | XXX TBD | (0, 0, 0, 1) | (u, v, 1, 1) |
2889 | | | [#envmap-bumpmap]_ | |
2890 +--------------------+--------------+--------------------+--------------+
2891 | Z | XXX TBD | (z, z, z, 1) | (0, z, 0, 1) |
2892 | | | [#depth-tex-mode]_ | |
2893 +--------------------+--------------+--------------------+--------------+
2894 | S | (s, s, s, s) | unknown | unknown |
2895 +--------------------+--------------+--------------------+--------------+
2897 .. [#envmap-bumpmap] http://www.opengl.org/registry/specs/ATI/envmap_bumpmap.txt
2898 .. [#depth-tex-mode] the default is (z, z, z, 1) but may also be (0, 0, 0, z)
2899 or (z, z, z, z) depending on the value of GL_DEPTH_TEXTURE_MODE.